Magnetic resonance imaging (MRI) is a bio-magnetic nuclear spin imaging technology developed rapidly along with the development of computer technology, electronic circuit technology, and superconductor technology. MRI allows precession hydrogen nuclei (e.g., H+) in a human tissue to carry out nutation by use of a magnetic field and a radio frequency (RF) pulse to generate a radio frequency signal, which is processed by a computer for imaging. When an object is placed in a magnetic field, the object is irradiated by an electromagnetic wave to make the object resonant. The released electromagnetic wave is analyzed to obtain locations and types of the nuclei constituting the object to thereby create a precise stereoscopic image of the interior of the object (e.g., an animation of consecutive slices, from the top to the base, of a human brain by scanning by magnetic resonance imaging).
During a magnetic resonance imaging test, magnetic resonance signals of the object under test are routed through a radio frequency receiving channel, such as a cable or an A/D converter, and finally reconstructed in a computing unit to form a magnetic resonance (MR) image for medical use. The radio frequency receiving channel may refer to a radio frequency channel between a receiving coil and a receiver in a magnetic resonance imaging apparatus. The radio frequency receiving channel is an important channel in a signal link, and attributes of the radio frequency receiving channel have a significant influence on image quality.
However, the non-linear features of the radio frequency receiving channel will cause distortion of magnetic resonance signals, and have a negative effect on the image quality of the magnetic resonance image. Since magnetic resonance signals are generally very weak, some switchable amplifiers may be installed in the radio frequency receiving channel, and will further deteriorate the non-linear features of the radio frequency receiving channel.